Method of manufacture for single crystal capacitor dielectric for a resonance circuit

ABSTRACT

A method of manufacturing an integrated circuit. This method includes forming an epitaxial material comprising single crystal piezo material overlying a surface region of a substrate to a desired thickness and forming a trench region to form an exposed portion of the surface region through a pattern provided in the epitaxial material. Also, the method includes forming a topside landing pad metal and a first electrode member overlying a portion of the epitaxial material and a second electrode member overlying the topside landing pad metal. Furthermore, the method can include processing the backside of the substrate to form a backside trench region exposing a backside of the epitaxial material and the landing pad metal and forming a backside resonator metal material overlying the backside of the epitaxial material to couple to the second electrode member overlying the topside landing pad metal.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/362,537 filed Nov. 28, 2016, now issued as U.S. Pat. No. 10,516,377,which is a divisional of U.S. patent application Ser. No. 14/298,076filed Jun. 6, 2014, now issued as U.S. Pat. No. 9,537,465 on Jan. 3,2017, which incorporates by reference, for all purposes, the followingconcurrently filed patent applications, all commonly owned: U.S. Pat.No. 9,673,364, issued Jun. 6, 2017 and U.S. Pat. No. 9,571,061 issuedFeb. 14, 2017.

BACKGROUND OF THE INVENTION

The present invention relates generally to electronic devices. Moreparticularly, the present invention provides techniques related to asingle crystal acoustic resonator. Merely by way of example, theinvention has been applied to a resonator device for a communicationdevice, mobile device, computing device, among others.

Mobile telecommunication devices have been successfully deployedworld-wide. Over a billion mobile devices, including cell phones andsmartphones, were manufactured in a single year and unit volumecontinues to increase year-over-year. With ramp of 4G/LTE in about 2012,and explosion of mobile data traffic, data rich content is driving thegrowth of the smartphone segment—which is expected to reach 2B per annumwithin the next few years. Coexistence of new and legacy standards andthirst for higher data rate requirements is driving RF complexity insmartphones. Unfortunately, limitations exist with conventional RFtechnology that is problematic, and may lead to drawbacks in the future.

From the above, it is seen that techniques for improving electronicdevices are highly desirable.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a single crystal acousticresonator. Merely by way of example, the invention has been applied to aresonator device for a communication device, mobile device, computingdevice, among others.

In an example, the present invention provides a single crystal capacitordielectric material configured on a substrate by a limited area epitaxy.The material is coupled between a pair of electrodes, which areconfigured from a topside and a backside of a substrate member, in anexample. In an example, the single crystal capacitor dielectric materialis provided using a metal-organic chemical vapor deposition, a molecularbeam epitaxy, an atomic layer deposition, a pulsed laser deposition, achemical vapor deposition, or a wafer bonding process. In an example,the limited area epitaxy is lifted-off the substrate and transferred toanother substrate. In an example, the material is characterized by adefect density of less than 1E+11 defects per square centimeter. In anexample, the single crystal capacitor material is selected from at leastone of AlN, AlGaN, InN, BN, or other group III nitrides. In an example,the single crystal capacitor material is selected from at least one of asingle crystal oxide including a high K dielectric, ZnO, or MgO.

In an example, a single crystal acoustic electronic device is provided.The device has a substrate having a surface region. The device has afirst electrode material coupled to a portion of the substrate and asingle crystal capacitor dielectric material having a thickness ofgreater than 0.4 microns and overlying an exposed portion of the surfaceregion and coupled to the first electrode material. In an example, thesingle crystal capacitor dielectric material is characterized by adislocation density of less than 10¹² defects/cm². A second electrodematerial is overlying the single crystal capacitor dielectric material.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the invention enables a cost-effectiveresonator device for communications applications. In a specificembodiment, the present device can be manufactured in a relativelysimple and cost effective manner. Depending upon the embodiment, thepresent apparatus and method can be manufactured using conventionalmaterials and/or methods according to one of ordinary skill in the art.The present device uses a gallium and nitrogen containing material thatis single crystalline. Depending upon the embodiment, one or more ofthese benefits may be achieved. Of course, there can be othervariations, modifications, and alternatives.

A further understanding of the nature and advantages of the inventionmay be realized by reference to the latter portions of the specificationand attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1 is a simplified diagram illustrating a surface single crystalacoustic resonator according to an example of the present invention.

FIG. 2 is a simplified diagram illustrating a bulk single crystalacoustic resonator according to an example of the present invention.

FIG. 3 is a simplified diagram illustrating a feature of a bulk singlecrystal acoustic resonator according to an example of the presentinvention.

FIG. 4 is a simplified diagram illustrating a piezo structure accordingto an example of the present invention.

FIG. 5 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention.

FIG. 6 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention.

FIG. 7 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention.

FIG. 8 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention.

FIG. 9 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention.

FIG. 10 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention.

FIG. 11 is a simplified diagram of a substrate member according to anexample of the present invention.

FIG. 12 is a simplified diagram of a substrate member according to anexample of the present invention.

FIG. 13 is a simplified table illustrating features of a conventionalfilter compared against the present examples according to examples ofthe present invention.

FIGS. 14-22 illustrate a manufacturing method for a single crystalacoustic resonator device in an example of the present invention.

FIG. 23 illustrates circuit diagrams of the single crystal acousticresonator device in an example of the present invention.

FIGS. 24-32 illustrate a manufacturing method for a single crystalacoustic resonator device in an example of the present invention.

FIG. 33 illustrates circuit diagrams of the single crystal acousticresonator device in an example of the present invention.

FIGS. 34 and 35 illustrate a reflector structure configured on thesingle crystal acoustic resonator device in an example of the presentinvention.

FIG. 36 illustrates circuit diagrams of the integrated reflectorstructure with the single crystal acoustic resonator device of theaforementioned Figures.

FIGS. 37 and 38 illustrate a reflector structure configured on thesingle crystal acoustic resonator device in an example of the presentinvention.

FIG. 39 illustrates circuit diagrams of the integrated reflectorstructure with the single crystal acoustic resonator device of theaforementioned Figures.

FIG. 40 illustrates simplified diagrams of a bottom surface region andtop surface region for the single crystal acoustic resonator device inan example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a single crystal acousticresonator. Merely by way of example, the invention has been applied to aresonator device for a communication device, mobile device, computingdevice, among others.

As additional background, the number of bands supported by smartphonesis estimated to grow by 7-fold compared to conventional techniques. As aresult, more bands mean high selectivity filter performance is becominga differentiator in the RF front end of smartphones. Unfortunately,conventional techniques have severe limitations.

That is, conventional filter technology is based upon amorphousmaterials and whose electromechanical coupling efficiency is poor (only7.5% for non-lead containing materials) leading to nearly half thetransmit power dissipated in high selectivity filters. In addition,single crystal acoustic wave devices are expected to deliverimprovements in adjacent channel rejection. Since there are twenty (20)or more filters in present smartphone and the filters are insertedbetween the power amplifier and the antenna solution, then there is anopportunity to improve the RF front end by reducing thermal dissipation,size of power amplifier while enhancing the signal quality of thesmartphone receiver and maximize the spectral efficiency within thesystem.

Utilizing single crystal acoustic wave device (herein after “SAW”device) and filter solutions, one or more of the following benefits maybe achieved: (1) large diameter silicon wafers (up to 200 mm) areexpected to realize cost-effective high performance solutions, (2)electromechanical coupling efficiency is expected to more than triplewith newly engineered strained piezo electric materials, (3) Filterinsertion loss is expected to reduce by 1 dB enabling longer batterylife, improve thermal management with smaller RF footprint and improvingthe signal quality and user experience. These and other benefits can berealized by the present device and method as further provided throughoutthe present specification, and more particularly below.

FIG. 1 is a simplified diagram illustrating a surface single crystalacoustic resonator according to an example of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. The present surface single crystal acousticresonator device 100 having a crystalline piezo material 120 overlying asubstrate 110 is illustrated. As shown, an acoustic wave propagates in alateral direction from a first spatial region to a second spatial regionsubstantially parallel to a pair of electrical ports 140, which form aninter-digital transducer configuration 130 with a plurality of metallines 131 that are spatially disposed between the pair of electricalports 140. In an example, the electrical ports on the left side can bedesignated for signal input, while the electrical ports on the rightside are designated for signal output. In an example, a pair ofelectrode regions are configured and routed to a vicinity of a planeparallel to a contact region coupled to the second electrode material.

In a SAW device example, surface acoustic waves produce resonantbehavior over a narrow frequency band near 880 MHz to 915 MHz frequencyband—which is a designated passband for a Europe, Middle East and Africa(EMEA) LTE enabled mobile smartphone. Depending on region of operationfor the communication device, there can be variations. For example, inNorth American transmit bands, the resonator can be designed such thatresonant behavior is near the 777 MHz to 787 MHz frequency passband.Other transmit bands, found in other regions, can be much higher infrequency, such as the Asian transmit band in the 2570 MHz to 2620 MHzpassband. Further, the examples provided here are for transmit bands. Insimilar fashion, the passband on the receiver side of the radio frontend also require similar performing resonant filters. Of course, therecan be variations, modifications, and alternatives.

Other characteristics of surface acoustic wave devices include thefundamental frequency of the SAW device, which is determined by thesurface propagation velocity (determined by the crystalline quality ofthe piezo-electric material selected for the resonator) divided by thewavelength (determined by the fingers in the interdigitated layout inFIG. 1). Measured propagation velocity (also referred to as SAWvelocity) in GaN of approximately 5800 m/s has been recorded, whilesimilar values are expected for AlN. Accordingly, higher SAW velocity ofsuch Group III-nitrides enables a resonator to process higher frequencysignals for a given device geometry.

Resonators made from Group III-nitrides are desirable as such materialsoperate at high power (leveraging their high critical electric field),high temperature (low intrinsic carrier concentration from their largebandgap) and high frequency (high saturated electron velocities). Suchhigh power devices (greater than 10 Watts) are utilized in wirelessinfrastructure and commercial and military radar systems to name a few.Further, stability, survivability and reliability of such devices arecritical for field deployment.

Further details of each of the elements provided in the present devicecan be found throughout the present specification and more particularbelow.

FIG. 2 is a simplified diagram illustrating a bulk single crystalacoustic resonator according to an example of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. The present bulk single crystal acoustic resonatordevice 200 having a crystalline piezo material is illustrated. As shown,an acoustic wave propagates in a vertical direction from a first spatialregion to a second spatial region between an upper electrode material231 and a substrate member 210. As shown, the crystalline piezo material220 is configured between the upper (231) and lower (232) electrodematerial. The top electrode material 231 is configured underneath aplurality of optional reflector layers, which are formed overlying thetop electrode 231 to form an acoustic reflector region 240.

In a bulk acoustic wave (hereinafter “BAW”) device example, acousticwaves produce resonant behavior over a narrow frequency band near 3600MHz to 3800 MHz frequency band—which is a designated passband for a LTEenabled mobile smartphone. Depending on region of operation for thecommunication device, there can be variations. For example, in NorthAmerican transmit bands, the resonator can be designed such thatresonant behavior is near the 2000 MHz to 2020 MHz frequency passband.Other transmit bands, found in other regions such as the Asian transmitband in the 2500 MHz to 2570 MHz passband. Further, the examplesprovided here are for transmit bands. In similar fashion, the passbandon the receiver side of the radio front end also require similarperforming resonant filters. Of course, there can be variations,modifications, and alternatives.

Other characteristics of single crystal BAW devices include theelectromechanical acoustic coupling in the device, which isproportionate to the piezoelectricity constant (influence by the designand strain of the single crystal piezo layer) divided by the acousticwave velocity (influenced by scattering and reflections in the piezomaterial). Acoustic wave velocity in GaN of over 5300 m/s has beenobserved. Accordingly, high acoustic wave velocity of such GroupIII-nitrides enables a resonator to process higher frequency signals fora given device geometry.

Similar to SAW devices, resonators made from Group III-nitrides aredesirable as such materials operate at high power (leveraging their highcritical electric field), high temperature (low intrinsic carrierconcentration from their large bandgap) and high frequency (highsaturated electron velocities). Such high power devices (greater than 10Watts) are utilized in wireless infrastructure and commercial andmilitary radar systems to name a few. Further, stability, survivabilityand reliability of such devices are critical for field deployment.

Further details of each of the materials provided in the present devicecan be found throughout the present specification and more particularbelow.

In an example, the device has a substrate, which has a surface region.In an example, the substrate can be a thickness of material, acomposite, or other structure. In an example, the substrate can beselected from a dielectric material, a conductive material, asemiconductor material, or any combination of these materials. In anexample, the substrate can also be a polymer member, or the like. In apreferred example, the substrate is selected from a material providedfrom silicon, a gallium arsenide, an aluminum oxide, or others, andtheir combinations.

In an example, the substrate is silicon. The substrate has a surfaceregion, which can be in an off-set or off cut configuration. In anexample, the surface region is configured in an off-set angle rangingfrom 0.5 degree to 1.0 degree. In an example, the substrate is <111>oriented and has high resistivity (greater than 10³ ohm-cm). Of course,there can be other variations, modifications, and alternatives.

In an example, the device has a first electrode material coupled to aportion of the substrate and a single crystal capacitor dielectricmaterial having a thickness of greater than 0.4 microns. In an example,the single crystal capacitor dielectric material has a suitabledislocation density. The dislocation density is less than 10¹²defects/cm², and greater than 10⁴ defects per cm², and variationsthereof. The device has a second electrode material overlying the singlecrystal capacitor dielectric material. Further details of each of thesematerials can be found throughout the present specification and moreparticularly below.

In an example, the single crystal capacitor material is a suitablesingle crystal material having desirable electrical properties. In anexample, the single crystal capacitor material is generally a galliumand nitrogen containing material such as a AlN, AlGaN, or GaN, amongInN, InGaN, BN, or other group III nitrides. In an example, the singlecrystal capacitor material is selected from at least one of a singlecrystal oxide including a high K dielectric, ZnO, MgO, or alloys ofMgZnGaInO. In an example, the high K is characterized by a defectdensity of less than 10¹² defects/cm², and greater than 10⁴ defects percm². Of course, there can be other variations, modifications, andalternatives.

In an example, the single crystal capacitor dielectric material ischaracterized by a surface region at least 50 micron by 50 micron, andvariations. In an example, the surface region can be 200 micron×200 umor as high as 1000 um×1000 um. Of course, there are variations,modifications, and alternatives.

In an example, the single crystal capacitor dielectric material isconfigured in a first strain state to compensate to the substrate. Thatis, the single crystal material is in a compressed or tensile strainstate in relation to the overlying substrate material. In an example,the strained state of a GaN when deposited on silicon is tensilestrained whereas an AlN layer is compressively strain relative to thesilicon substrate.

In a preferred example, the single crystal capacitor dielectric materialis deposited overlying an exposed portion of the substrate. In anexample, the single crystal capacitor dielectric is lattice mismatchedto the crystalline structure of the substrate, and may be straincompensated using a compressively strain piezo nucleation layer such asAlN or SiN.

In an example, the device has the first electrode material is configuredvia a backside of the substrate. In an example, the first electrodematerial is configured via a backside of the substrate. Theconfiguration comprises a via structure configured within a thickness ofthe substrate.

In an example, the electrode materials can be made of a suitablematerial or materials. In an example, each of the first electrodematerial and the second electrode material is selected from a refractorymetal or other precious metals. In an example, each of the firstelectrode material and the second electrode material is selected fromone of tantalum, molybdenum, platinum, titanium, gold, aluminumtungsten, or platinum, combinations thereof, or the like.

In an example, the first electrode material and the single crystalcapacitor dielectric material comprises a first interface regionsubstantially free from an oxide bearing material. In an example, thefirst electrode material and the single crystal capacitor dielectricmaterial comprises a second interface region substantially free from anoxide bearing material. In an example, the device can include a firstcontact coupled to the first electrode material and a second contactcoupled to the second electrode material such that each of the firstcontact and the second contact are configured in a co-planararrangement.

In an example, the device has a reflector region configured to the firstelectrode material. In an example, the device also has a reflectorregion configured to the second electrode material. The reflector regionis made of alternating low impedance (e.g. dielectric) andhigh-impedance (e.g. metal) reflector layers, where each layer istargeted at one quarter-wave in thickness, although there can bevariations.

In an example, the device has a nucleation material provided between thesingle crystal capacitor dielectric material and the first electrodematerial. The nucleation material is typically AlN or SiN.

In an example, the device has a capping material provided between thesingle crystal capacitor dielectric material and the second electrodematerial. In an example, the capping material is GaN.

In an example, the single crystal capacitor dielectric materialpreferably has other properties. That is, the single crystal capacitordielectric material is characterized by a FWHM of less than one degree.

In an example, the single crystal capacitor dielectric is configured topropagate a longitudinal signal at an acoustic velocity of 5000meters/second and greater. In other embodiments where strain isengineered, the signal can be over 6000 m/s and below 12,000 m/s. Ofcourse, there can be variations, modifications, and alternatives.

The device also has desirable resonance behavior when tested using atwo-port network analyzer. The resonance behavior is characterized bytwo resonant frequencies (called series and parallel)—whereby oneexhibits an electrical impedance of infinity and the other exhibits animpedance of zero. In between such frequencies, the device behavesinductively. In an example, the device has s-parameter derived from atwo-port analysis, which can be converted to impedance. From s11parameter, the real and imaginary impedance of the device can beextracted. From s21, the transmission gain of the resonator can becalculated. Using the parallel resonance frequency along the known piezolayer thickness, the acoustic velocity can be calculated for the device.

FIG. 3 is a simplified diagram illustrating a feature of a bulk singlecrystal acoustic resonator according to an example of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. As shown, diagram 300 shows the presentinvention applied as a band pass filter for RF signals. A specificfrequency range is allowed through the filter, as depicted by thedarkened block elevated from the RF spectrum underneath the wavelengthillustration. This block is matched to the signal allowed through thefilter in the illustration above. Single crystal devices can offerbetter acoustic quality versus BAW devices due to lower filter loss andrelieving the specification requirements on the power amplifier. Thesecan result benefits for devices utilizing the present invention such asextended battery, efficient spectrum use, uninterrupted callerexperience, and others.

FIG. 4 is a simplified diagram illustrating a piezo structure accordingto an example of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. In anexample, the structure 400 is configured on a bulk substrate member 410,including a surface region. In an example, the single crystal piezomaterial epitaxial 420 is formed using a growth process. The growthprocess can include chemical vapor deposition, molecular beam epitaxialgrowth, or other techniques overlying the surface of the substrate. Inan example, the single crystal piezo material can include single crystalgallium nitride (GaN) material, single crystal Al(x)Ga(1-x)N where0<x<1.0 (x=“Al mole fraction”) material, single crystal aluminum nitride(AlN) material, or any of the aforementioned in combination with eachother. Of course, there can also be modifications, alternatives, andvariations. Further details of the substrate can be found throughout thepresent specification, and more particularly below.

FIG. 5 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. In an example, the structure 500 is configured overlying anucleation region 530, which is overlying a surface of the substrate510. In an example, the nucleation region 530 is a layer or can bemultiple layers. The nucleation region is made using a piezo-electricmaterial in order to enable acoustic coupling in a resonator circuit. Inan example, the nucleation region is a thin piezo-electric nucleationlayer, which may range from about 0 to 100 nm in thickness, may be usedto initiate growth of single crystal piezo material 520 overlying thesurface of the substrate. In an example, the nucleation region can bemade using a thin SiN or AlN material, but can include variations. In anexample, the single crystal piezo material has a thickness that canrange from 0.2 um to 20 um, although there can be variations. In anexample, the piezo material that has a thickness of about 2 um istypical for 2 GHz acoustic resonator device. Further details of thesubstrate can be found throughout the present specification, and moreparticularly below.

FIG. 6 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. In an example, the structure 600 is configured using a GaN piezomaterial 620. In an example, each of the regions are single crystal orsubstantially single crystal. In an example, the structure is providedusing a thin AlN or SiN piezo nucleation region 630, which can be alayer or layers. In an example, the region is unintentional doped (UID)and is provided to strain compensate GaN on the surface region of thesubstrate 610. In an example, the nucleation region has an overlying GaNsingle crystal piezo region (having Nd-Na: between 10¹⁴/cm3 and10¹⁸/cm3), and a thickness ranging between 1.0 um and 10 um, althoughthere can be variations. Further details of the substrate can be foundthroughout the present specification, and more particularly below.

FIG. 7 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. As shown, the structure 700 is configured using an AlN piezomaterial 720. Each of the regions is single-crystal or substantiallysingle crystal. In an example, the structure is provided using a thinAlN or SiN piezo nucleation region 730, which can be a layer or layers.In an example, the region is unintentional doped (UID) and is providedto strain compensate AlN on the surface region of the substrate 710. Inan example, the nucleation region has an overlying AlN single crystalpiezo region (having Nd-Na: between 10¹⁴/cm3 and 10¹⁸/cm3), and athickness ranging between 1.0 um and 10 um, although there can bevariations. Further details of the substrate can be found throughout thepresent specification, and more particularly below.

FIG. 8 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. As shown, the structure 800 is configured using an AlGaN piezomaterial 820. Each of the regions is single-crystal or substantiallysingle crystal. In an example, the structure is provided using a thinAlN or SiN piezo nucleation region 830, which can be a layer or layers.In an example, the region is unintentional doped (UID) and is providedto strain compensate AlN on the surface region of the substrate 810. Inan example, the AlGaN single crystal piezo layer where Al(x)Ga(1-x)N hasAl mole composition 0<x<1.0, (Nd-Na: between 10¹⁴/cm3 and 10¹⁸/cm3), athickness ranging between 1 um and 10 um, among other features. Furtherdetails of the substrate can be found throughout the presentspecification, and more particularly below.

FIG. 9 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. The structure 900 is configured using an AlN/AlGaN piezomaterial 920. Each of the regions is single-crystal or substantiallysingle crystal. In an example, the structure is provided using a thinAlN or SiN piezo nucleation region 930, which can be a layer or layers.In an example, the region is unintentional doped (UID) and is providedto strain compensate AlN on the surface region of the substrate 910. Inan example, one or more alternating stacks are formed overlying thenucleation region. In an example, the stack includes AlGaN/AlN singlecrystal piezo layer where Al(x)Ga(1-x)N has Al mole composition 0<x<1.0;(Nd-Na: between 1014/cm3 and 1018/cm3), a thickness ranging between 1.0um and 10 um; a AlN (1 nm<thickness<30 nm) serves to strain compensatelattice and allow thicker AlGaN piezo layer. In an example, the finalsingle crystal piezo layer is AlGaN. In an example, the structure has atotal stack thickness of at least 1 um and less than 10 um, amongothers. Further details of the substrate can be found throughout thepresent specification, and more particularly below.

FIG. 10 is a simplified diagram illustrating a piezo structure accordingto an alternative example of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. As shown, the structure 1000 has an optional GaN piezo-electriccap layer or layers 1040. In an example, the cap layer 1040 or regioncan be configured on any of the aforementioned examples, among others.In an example, the cap region can include at least one or more benefits.Such benefits include improved electro-acoustic coupling from topsidemetal (electrode 1) into piezo material, reduced, surface oxidation,improved manufacturing, among others. In an example, the GaN cap regionhas a thickness ranging between 1 nm-10 nm, and has Nd-Na: between10¹⁴/cm3 and 10¹⁸/cm3, although there can be variations. Further detailsof the substrate can be found throughout the present specification, andmore particularly below.

FIG. 11 is a simplified diagram of a substrate member according to anexample of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. In an example,the single crystal acoustic resonator material 1120 can be a singlecrystal piezo material epitaxial grown (using CVD or MBE technique) on asubstrate 1110. The substrate 1110 can be a bulk substrate, a composite,or other member. The bulk substrate 1110 is preferably gallium nitride(GaN), silicon carbide (SiC), silicon (Si), sapphire (Al2O3), aluminumnitride (AlN), combinations thereof, and the like.

FIG. 12 is a simplified diagram of a substrate member according to anexample of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims. In an example,the single crystal acoustic resonator material 1220 can be a singlecrystal piezo material epitaxial grown (using CVD or MBE technique) on asubstrate 1210. The substrate 1210 can be a bulk substrate, a composite,or other member. The bulk substrate 1210 is preferably gallium nitride(GaN), silicon carbide (SiC), silicon (Si), sapphire (Al2O3), aluminumnitride (AlN), combinations thereof, and the like. In an example, thesurface region of the substrate is bare and exposed crystallinematerial.

FIG. 13 is a simplified table illustrating features of a conventionalfilter compared against the present examples according to examples ofthe present invention. As shown, the specifications of the “PresentExample” versus a “Conventional” embodiment are shown with respect tothe criteria under “Filter Solution”.

In an example, the GaN, SiC and Al2O3 orientation is c-axis in order toimprove or even maximize a polarization field in the piezo-electricmaterial. In an example, the silicon substrate orientation is <111>orientation for same or similar reason. In an example, the substrate canbe off-cut or offset. While c-axis or <111> is nominal orientation, anoffcut angle between +/−1.5 degrees may be selected for one or more ofthe following reasons: (1) controllability of process; (2) maximizationof K2 of acoustic resonator, and other reasons. In an example, thesubstrate is grown on a face, such as a growth face. A Ga-face ispreferred growth surface (due to more mature process). In an example,the substrate has a substrate resistivity that is greater than 104ohm-cm, although there can be variations. In an example, the substratethickness ranges 100 um to 1 mm at the time of growth of single crystalpiezo deposition material. Of course, there can be variations,modifications, and alternatives.

As used herein, the terms “first” “second” “third” and “nth” shall beinterpreted under ordinary meaning. Such terms, alone or together, donot necessarily imply order, unless understood that way by one ofordinary skill in the art. Additionally, the terms “top” and “bottom”may not have a meaning in reference to a direction of gravity, whileshould be interpreted under ordinary meaning. These terms shall notunduly limit the scope of the claims herein.

As used herein, the term substrate is associated with Group III-nitridebased materials including GaN, InGaN, AlGaN, or other Group iiicontaining alloys or compositions that are used as starting materials,or AlN or the like. Such starting materials include polar GaN substrates(i.e., substrate where the largest area surface is nominally an (h k L)plane wherein h=k=0, and 1 is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k l) plane wherein 1=0, and at least oneof h and k is non-zero) or semi-polar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k l) plane wherein 1=0, and atleast one of h and k is non-zero).

As shown, the present device can be enclosed in a suitable package. Asan example, the packaged device can include any combination of elementsdescribed above, as well as outside of the present specification. Asused herein, the term “substrate” can mean the bulk substrate or caninclude overlying growth structures such as a gallium and nitrogencontaining epitaxial region, or functional regions, combinations, andthe like.

In an example, the present disclosure provides a step-by-stepfabrication of a single-crystal acoustic resonator (SCAR) device.Additionally, the disclosure provides fabrication processes tomanufacture two or more resonators together to provide a SCAR filter,among other devices. In an example, the present processes can beimplemented using conventional high volume wafer fabrication facilitiesfor efficient operations, and competitive costs. Of course, there can beother variations, modifications, and alternatives.

FIGS. 14-22 illustrate a manufacturing method for a single crystalacoustic resonator device in an example of the present invention. Theseillustrations are merely examples, and should not unduly limit the scopeof the claims herein.

Referring to the Figures, an example of a manufacturing process can bebriefly described below:

-   -   1. Start;    -   2. Provide a substrate member, e.g., 150 mm or 200 mm diameter        material, having a surface region;    -   3. Treat the surface region;    -   4. Form an epitaxial material comprising single crystal piezo        material overlying the surface region to a desired thickness;    -   5. Pattern the epitaxial material using a masking and etching        process to form a trench region by causing formation of an        exposed portion of the surface region through a pattern provided        in the epitaxial material;    -   6. Form topside landing pad metal, which may include a stack        that has a metal layer that reacts slowly with etchants in a        backside substrate etching process, as defined below;    -   7. Form topside electrode members, including a first electrode        member overlying a portion of the epitaxial material, and a        second electrode member overlying the topside landing pad metal;    -   8. Mask and remove (via etching) a portion of the substrate from        the backside to form a first trench region exposing a backside        of the epitaxial material overlying the first electrode member,        and a second trench region exposing a backside of the landing        pad metal;    -   9. Form backside resonator metal material for the second        electrode overlying the exposed portion of the epitaxial        material (or piezo membrane) to form a connection from the        epitaxial material to the backside of the landing pad metal        coupled to the second electrode member overlying the topside        landing pad metal;    -   10. Form resonator active area using a masking and etching        process, while electrically and spatially isolating the first        electrode member from the second electrode member on the top        side, while also fine tuning the resonance capacitor;    -   11. Form overlying thickness of protecting dielectric material        (e.g., SiO2, SiN) overlying an upper surface region on topside        surface; and    -   12. Perform other steps, as desired.

The aforementioned steps are provided for the formation of a resonatordevice using a single crystal capacitor dielectric. As shown, a pair ofelectrode members is configured to provide for contact from one side ofthe device. One of the electrode members uses a backside contact, whichis coupled to a metal stack layer to configure the pair of electrodes.Of course, depending upon the embodiment, steps or a step can be added,removed, combined, reordered, or replaced, or has other variations,alternatives, and modifications. Further details of the presentmanufacturing process can be found throughout the present specification,and more particularly below.

As shown in FIG. 14, the method begins by providing a substrate member1410. The substrate member has a surface region. In an example, thesubstrate member thickness (t) is 400 um, which can have a diameter of150 mm or 200 mm diameter material, although there can be variationsfrom 50 mm to 300 mm.

In an example, the surface region of the substrate member is treated.The treatment often includes cleaning and/or conditioning. In anexample, the treatment occurs in an MOCVD or LPCVD reactor with ammoniagas flowing at high temperature (e.g. in the range from 940° C. to 1100°C.) at a pressure ranging from one-tenth of an atmosphere to oneatmosphere. Depending upon the embodiment, other treatment processes canalso be used.

In an example, the method includes formation of an epitaxial materialcomprising single crystal piezo material 1420 overlying the surfaceregion to a desired thickness, as shown. Using a configuration ofTrimethylgallium (TMG), Trimethylaluminium (TMA), ammonia (NH₃) andhydrogen (H₂) gases, the epitaxial material is grown under hightemperature in the range of 940° C. to 1100° C. in an atmosphericcontrolled environment using a MOCVD or LPCVD growth apparatus to athickness ranging from 0.4 um to 7.0 um, depending on target resonancefrequency of the capacitor device. The material also has a defectdensity of 10⁴ to 10¹² per cm², although there can be variations.

In an example, the epitaxial material 1521 is patterned (FIG. 15).Patterning involves a masking and etching process. The mask is often 1-3um of photoresist. Etching uses chlorine-based chemistries (gases mayinclude BCl₃, Cl₂, and/or argon) in an RIE or ICP etch tool, undercontrolled temperature and pressure conditions to adjust the etch rateand sidewall profile. The patterning forms a trench region (or viastructure) by causing formation of an exposed portion of the surfaceregion through a pattern provided in the epitaxial material.

In an example, the method forms a topside landing pad metal 1630 (FIG.16), which may include a stack that has a metal layer that reacts slowlywith etchants in a backside substrate etching process, as defined below.In an example, the metal is a refractory metal (such as tantalum,molybdenum, tungsten) or other metal (such as gold, aluminum, titaniumor platinum). The metal is used subsequently as a stop region for abackside etch process, as noted.

In an example, the method forms a topside metal structure (FIG. 17). Thestructure has topside electrode members, including a first electrodemember 1741 overlying a portion of the epitaxial material, and a secondelectrode member 1742 overlying the topside landing pad metal, as shown.The metal structure is made using a refractory metal (such as tantalum,molybdenum, tungsten), and has a thickness of 300 nm, chosen to definethe resonant frequency of the capacitor device.

In an example, the method performs backside processing (FIG. 18), byflipping the substrate top-side down. In an example, the method includesa patterning process of the backside of the substrate. The process usesa mask and removal process via etching a portion of the substrate 1811from the backside to form a first trench region exposing a backside ofthe epitaxial material overlying the first electrode member, and asecond trench region exposing a backside of the landing pad metal. In anexample, etching is performed using chlorine-based gas in either an RIEor ICP reactor with temperature and pressure defined to control etchrate, selectivity and sidewall slope.

Next, the method includes formation of a backside resonator metalmaterial 1943 (FIG. 19) for the second electrode overlying the exposedportion of the epitaxial material (or piezo membrane) to form aconnection from the epitaxial material to the backside of the landingpad metal coupled to the second electrode member overlying the topsidelanding pad metal.

As shown, the piezo membrane 1921 is sandwiched between the pair ofelectrodes, which are configured from the top-side and backside of thesubstrate member 1911. The member is <111> oriented silicon substratewith a resistivity of greater than 10 ohm-cm.

In an example, the method forms or patterns the resonator active area2022 using a masking and etching process (FIG. 20). The end objective isto electrically and spatially isolate the first electrode member fromthe second electrode member on the top side, while also fine tuning theresonance capacitor. In an example, the resonator active area is 200 umby 200 um. The patterning uses chlorine-based RIE or ICP etchingtechnique.

The method forms a thickness of protecting material 2150 (FIG. 21). Inan example, the method forms a combination of silicon dioxide, whichforms a conforming structure, and an overlying silicon nitride cappingmaterial. The silicon dioxide and silicon nitride materials are formedusing a combination of silane, nitrogen and oxygen sources and depositedusing a PECVD chamber.

The method forms a first and second electrode (2261, 2262) that areelectrically coupled to the first top electrode 2241 and second topelectrode 2242, respectively (FIG. 22). The intrinsic device is markedas 2201. In an example, the method also may include other steps or othermaterials, as desirable.

In an example, the present method can also include one or more of theseprocesses for formation of the upper electrode structures, passivationmaterial, and backside processing. In an example, the present substrateincluding overlying structures can include a surface clean using HCl:H2O(1:1) for a predetermined amount of time, followed by rinse and loadinto sputtering tool.

In the sputtering tool to form the electrode metallization, the methodincludes a molybdenum (Mo) metal (3000 Å) blanket deposition usingsputtering technique on an exposed top side of the single crystal piezomaterial. In an example, if desired, a thin titanium adhesion metal(<100 Å) can be deposited prior to formation of the Mo metal. Suchtitanium metal serves as a glue layer, among other features. In anexample, the method performs a mask and pattern process to etch away Moin field areas (leaving Mo in probe pad, coplanar waveguide (CPW)interconnect, top-plate/first electrode, via landing pad/secondelectrode, and alignment mark areas. In an example, titanium-aluminum(100 Å/4 um) is deposited on Mo metal in probe pad and CPW areas. In anexample, Ti/Al is formed on the landing pad for subsequently depositedcopper-tin metal pillars for wafer-level flip-chip package—CuSn pillarsand die sawing are deposited. In an example, the method forms adielectric passivation (25 um of Spin-on Polymer photo-dielectric(ELECTRA WLP SH32-1-1) of top-side surface, or alternatively acombination of SiN or SiO2 is formed overlying the top surface.

In an example, the method includes patterning to open bond pads andprobe pads by exposing photo-dielectric and developing away dielectricmaterial on pads. The patterning process completes an upper region ofthe substrate structure, before backside processing is performed.Further details of the present method can be found throughout thepresent specification, and more particularly below.

In an example, the substrate is provided on a flip mount wafer and mount(using photoresist) onto a carrier wafer to begin backside process. Inan example, the backside processing uses a multi-step (e.g., two step)process. In an example, the wafer is thinned from about 500 um to about300 um and less using backside grinding process, which may also includepolishing, and cleaning. In an example, the backside is coated withmasking material, such as photoresist, and patterned to open trenchregions for the piezo material and the landing pad regions. In anexample, the method incudes a shallow etch process into the substrate,which can be silicon for example. In an example, the method coats thebackside with photoresist to open and expose a backside region of thepiezo material, which exposes a full membrane area, which includesenclosed the piezo material and the landing pad areas. In an example,the method also performs an etch until the piezo material and thelanding pads are exposed. In an example, the “rib” support is featurewhich results from 2-step process, although there can be variations, asfurther described below.

In an example, the backside is patterned with photoresist to align thebackside pad metal (electrode #2), interconnect and landing pad. In anexample, the backside is treated using a cleaning process using diluteHCL:H2O (1:1), among other suitable processes. In an example, the methodalso includes deposition of about 3000 Å of Mo metal in selective areas,provided that the backside of the wafer is patterned with metal in aselective manner and not blanket deposition. In an example, the metal isformed to reduce parasitic capacitance and enables routing of backsidefor circuit implementation, which is beneficial for different circuitnode interconnections. In an example, if desired, a thin titaniumadhesion metal (<100 Å) can be deposited prior to Mo as a glue material.

In an example, the method also includes formation of a dielectricpassivation (25 um of spin-on polymer photo-dielectric (e.g., ELECTRAWLP SH32-1-1) of backside side surface for mechanical stability. In anexample in an alternative example, the method includes deposition of SiNand/or SiO2 to fill the backside trench region to provide suitableprotection, isolation, and provide other features, if desired.

In an example, the method then separates and/or unmounts the completedsubstrate for transfer into a wafer carrier. The completed substrate hasthe devices, and overlying protection materials. In an example, thesubstrate is now ready for saw and break, and other backend processessuch as wafer level packaging, or other techniques. Of course, there canbe other variations, modifications, and alternatives.

FIG. 23 illustrates circuit diagrams of the single crystal acousticresonator device in an example of the present invention. Thisillustration is merely an example, and should not unduly limit the scopeof the claims herein. Circuit 2301 shows a block diagram with the piezomembrane 2322 sandwiched between the first top electrode 2361 and thesecond top electrode 2362. The connection area 2303 of block diagram2301 is represented in the circuit diagram 2302, showing an equivalentcircuit configuration.

FIGS. 24-32 illustrate a manufacturing method for a single crystalacoustic resonator device in an example of the present invention. Thisillustration is merely an example, and should not unduly limit the scopeof the claims herein.

An example of an alternative manufacturing process can be brieflydescribed below:

-   -   1. Start;    -   2. Provide a substrate member, e.g., 150 mm or 200 mm diameter        material, having a surface region;    -   3. Treat the surface region to prepare for epitaxial growth;    -   4. Form an epitaxial material comprising single crystal piezo        material overlying the surface region to a desired thickness;    -   5. Pattern the epitaxial material using a masking and etching        process to form a trench region by causing formation of an        exposed portion of the surface region through a pattern provided        in the epitaxial material; alternatively, the patterning of the        epitaxial material may also occur using a laser drill technique;    -   6. Form topside landing pad metal, which may include a stack        that has a metal layer that reacts slowly with etchants in a        backside substrate etching process, as defined below;    -   7. Form topside electrode members, including a first electrode        member overlying a portion of the epitaxial material, and a        second electrode member overlying the topside landing pad metal;    -   8. Mask and remove (via etching) a portion of the substrate from        the backside to form a single trench region exposing a backside        of the epitaxial material overlying the first electrode member,        and exposing a backside of the landing pad metal; a shallow        “rib” structure may be formed using a two-step mask and etch        process with the goal of providing mechanical support to the        epitaxial material;    -   9. Form backside resonator metal material for the second        electrode overlying the exposed portion of the epitaxial        material (or piezo membrane) to form a connection from the        epitaxial material to the backside of the landing pad metal        coupled to the second electrode member overlying the topside        landing pad metal;    -   10. Form resonator active area with low surface leakage current        using a passivation process, which electrically and spatially        isolates the first electrode member from the second electrode        member on the top side, while also fine tuning the resonance        capacitor; a dielectric passivation layer (such as SiN or SiO2)        is deposited using PECVD technique using silane gas in a        controlled temperature and pressure environment to control        dielectric index of refraction;    -   11. Form overlying thickness of protecting dielectric material        (options include SiO2, SiN, or spin-on polymer coating)        overlying an upper surface region on topside surface; and    -   12. Perform other steps, as desired.

The aforementioned steps are provided for the formation of a resonatordevice using a single crystal capacitor dielectric. As shown, a pair ofelectrode members is configured to provide for contact from one side ofthe device. One of the electrode members uses a backside contact, whichis coupled to a metal stack layer to configure the pair of electrodes.Of course, depending upon the embodiment, steps or a step can be added,removed, combined, reordered, or replaced, or has other variations,alternatives, and modifications. Further details of the presentmanufacturing process can be found throughout the present specification,and more particularly below.

As shown in FIG. 24, the method begins by providing a substrate member2410. The substrate member has a surface region. In an example, thesubstrate member thickness is 400 um, which can have a diameter of 150mm or 200 mm diameter material, although there can be variations from 50mm to 300 mm.

In an example, the surface region of the substrate member is treated.The treatment often includes cleaning and/or conditioning. In anexample, the treatment occurs in an MOCVD or LPCVD reactor with ammoniagas flowing at high temperature (e.g. in the range from 940° C. to 1100°C.) at a pressure ranging from one-tenth of an atmosphere to oneatmosphere.

In an example, the method includes formation of an epitaxial materialcomprising single crystal piezo material 2420 overlying the surfaceregion to a desired thickness (t), as shown. Using a configuration ofTrimethylgallium (TMG), Trimethylaluminium (TMA), ammonia (NH₃) andhydrogen (H₂) gases, the epitaxial material is grown under hightemperature in the range of 940° C. to 1100° C. in an atmosphericcontrolled environment using a MOCVD or LPCVD growth apparatus to athickness ranging from 0.4 um to 7.0 um, depending on target resonancefrequency of the capacitor device. The material also has a defectdensity of 10⁴ to 10¹² per cm².

In an example, the epitaxial material 2521 is patterned (FIG. 25).Patterning involves a masking and etching process. The mask is often 1-3um of photoresist. Etching uses chlorine-based chemistries (gases mayinclude BCl₃, Cl₂, and/or argon) in an RIE or ICP etch tool, undercontrolled temperature and pressure conditions to adjust the etch rateand sidewall profile. The patterning forms a trench region (or viastructure) by causing formation of an exposed portion of the surfaceregion through a pattern provided in the epitaxial material.

In an example, the method forms a topside landing pad metal 2630 (FIG.26), which may include a stack that has a metal layer that reacts slowlywith etchants in a backside substrate etching process, as defined below.In an example, the metal is a refractory metal (such as tantalum,molybdenum, tungsten) or other metal (such as gold, aluminum, titaniumor platinum). The metal is used subsequently as a stop region for abackside etch process, as noted.

In an example, the method forms a topside metal structure (FIG. 27). Thestructure has topside electrode members, including a first electrodemember 2741 overlying a portion of the epitaxial material, and a secondelectrode member 2742 overlying the topside landing pad metal, as shown.The metal structure is made using a refractory metal (such as tantalum,molybdenum, tungsten), and has a thickness of 300 nm, chosen to definethe resonant frequency of the capacitor device.

In an example, the method performs backside processing (FIG. 28), byflipping the substrate top-side down. In an example, the method includesa patterning process of the backside of the substrate 2811. The processuses a mask and removal process via etching a portion of the substratefrom the backside to form a first trench region exposing a backside ofthe epitaxial material overlying the first electrode member, and asecond trench region exposing a backside of the landing pad metal. Asupport member 2812 can be configured between the two trench regions. Inan example, the support member can be recessed from a bottom sidesurface region, although there can be variations. In an example, etchingis performed using chlorine-based gas in either an RIE or ICP reactorwith temperature and pressure defined to control etch rate, selectivityand sidewall slope.

Next, the method includes formation of a backside resonator metalmaterial 2943 (FIG. 29) for the second electrode overlying the exposedportion of the epitaxial material (or piezo membrane) to form aconnection from the epitaxial material to the backside of the landingpad metal coupled to the second electrode member overlying the topsidelanding pad metal.

As shown, the piezo membrane 2921 is sandwiched between the pair ofelectrodes, which are configured from the top-side and backside of thesubstrate member. The member is <111> oriented silicon substrate with aresistivity of greater than 10 ohm-cm.

In an example, the method forms or patterns the resonator active areausing a masking and etching process. The end objective is toelectrically and spatially isolate the first electrode member from thesecond electrode member on the top side, while also fine tuning theresonance capacitor. In an example, the resonator active area is 200 umby 200 um. The patterning uses chlorine-based RIE or ICP etchingtechnique.

The method forms a passivation layer 3050 (FIG. 30) and a thickness ofprotecting material 3170 (FIG. 31). In an example, the method forms acombination of silicon dioxide, which forms a conforming structure, andan overlying silicon nitride capping material. The silicon dioxide andsilicon nitride materials are formed using a combination of silane,nitrogen and oxygen sources and deposited using a PECVD chamber.

The method forms a first and second electrode (3261, 3262) that areelectrically coupled to the first top electrode 3241 and second topelectrode 3242, respectively (FIG. 32). The intrinsic device is markedas 3201. In an example, the method also may include other steps or othermaterials, as desirable.

In an example, the present method can also include one or more of theseprocesses for formation of the upper electrode structures, passivationmaterial, and backside processing. In an example, the present substrateincluding overlying structures can include a surface clean using HCl:H2O(1:1) for a predetermined amount of time, followed by rinse and loadinto sputtering tool.

In the sputtering tool to form the electrode metallization, the methodincludes a molybdenum (Mo) metal (3000 Å) blanket deposition usingsputtering technique on an exposed top side of the single crystal piezomaterial. In an example, if desired, a thin titanium adhesion metal(<100 Å) can be deposited prior to formation of the Mo metal. Suchtitanium metal serves as a glue layer, among other features. In anexample, the method performs a mask and pattern process to etch away Moin field areas (leaving Mo in probe pad, coplanar waveguide (CPW)interconnect, top-plate/first electrode, via landing pad/secondelectrode, and alignment mark areas. In an example, titanium-aluminum(100 Å/4 um) is deposited on Mo metal in probe pad and CPW areas. In anexample, Ti/Al is formed on the landing pad for subsequently depositedcopper-tin metal pillars for wafer-level flip-chip package—CuSn pillarsand die sawing are deposited. In an example, the method forms adielectric passivation (25 um of Spin-on Polymer photo-dielectric(ELECTRA WLP SH32-1-1) of top-side surface, or alternatively acombination of SiN or SiO2 is formed overlying the top surface.

In an example, the method includes patterning to open bond pads andprobe pads by exposing photo-dielectric and developing away dielectricmaterial on pads. The patterning process completes an upper region ofthe substrate structure, before backside processing is performed.Further details of the present method can be found throughout thepresent specification, and more particularly below.

In an example, the substrate is provided on a flip mount wafer and mount(using photoresist) onto a carrier wafer to begin backside process. Inan example, the backside processing uses a multi-step (e.g., two step)process. In an example, the wafer is thinned from about 500 um to about300 um and less using backside grinding process, which may also includepolishing, and cleaning. In an example, the backside is coated withmasking material, such as photoresist, and patterned to open trenchregions for the piezo material and the landing pad regions. In anexample, the method incudes a shallow etch process into the substrate,which can be silicon for example. In an example, the method coats thebackside with photoresist to open and expose a backside region of thepiezo material, which exposes a full membrane area, which includesenclosed the piezo material and the landing pad areas. In an example,the method also performs an etch until the piezo material and thelanding pads are exposed. In an example, the “rib” support is featurewhich results from 2-step process, although there can be variations.

In an example, the backside is patterned with photoresist to align thebackside pad metal (electrode #2), interconnect and landing pad. In anexample, the backside is treated using a cleaning process using diluteHCl:H2O (1:1), among other suitable processes. In an example, the methodalso includes deposition of about 3000 A of Mo metal in selective areas,provided that the backside of the wafer is patterned with metal in aselective manner and not blanket deposition. In an example, the metal isformed to reduce parasitic capacitance and enables routing of backsidefor circuit implementation, which is beneficial for different circuitnode interconnections. In an example, if desired, a thin titaniumadhesion metal (<100 Å) can be deposited prior to Mo as a glue material.

In an example, the method also includes formation of a dielectricpassivation (25 um of spin-on polymer photo-dielectric (e.g., ELECTRAWLP SH32-1-1) of backside side surface for mechanical stability. In anexample in an alternative example, the method includes deposition of SiNand/or SiO2 to fill the backside trench region to provide suitableprotection, isolation, and provide other features, if desired.

In an example, the method then separates and/or unmounts the completedsubstrate for transfer into a wafer carrier. The completed substrate hasthe devices, and overlying protection materials. In an example, thesubstrate is now ready for saw and break, and other backend processessuch as wafer level packaging, or other techniques. Of course, there canbe other variations, modifications, and alternatives.

FIG. 33 illustrates circuit diagrams of the single crystal acousticresonator device in an example of the present invention. Thisillustration is merely an example, and should not unduly limit the scopeof the claims herein. Circuit 3301 shows a block diagram with the piezomembrane 3322 sandwiched between the first top electrode 3361 and thesecond top electrode 3362. The connection area 3303 of block diagram3301 is represented in the circuit diagram 3302, showing an equivalentcircuit configuration.

In an example, the present disclosure illustrations an acousticreflector structure which can be added, only if needed, or desirable. Inan example, the acoustic reflector on a single crystal acousticresonator device (SCAR) device can provide improved acoustic coupling,so called K². In conventional BAW devices, an acoustic resonator isinserted into substrate/carrier material, which may be cumbersome andnot efficient, although used. In an example, because a portion of thesubstrate is removed from backside of single crystal piezo material fromthe device, then the acoustic reflector is likely not needed or desiredon either side of the acoustic resonator. However, in contrast toconventional bulk acoustic wave devices where reflector is integratedinto the substrate, the acoustic reflector is integrated on the topsideof the device where is can serve two functions: (i) reduce moisturesensitivity to SCAR device, AND (ii) provide acoustic isolation fromfilter device and surrounding environment (similar to a Faraday cage),among other functions. These and other features can be found throughoutthe present specification and more particularly below.

FIGS. 34 and 35 illustrate a reflector structure (3400, 3500) configuredon the single crystal acoustic resonator device in an example of thepresent invention. As shown, the device has similar features as one ofthe prior examples (FIGS. 14-22). Additionally, the device is configuredwith a reflector structure including alternating quarter-wave layers ofhigh acoustic impedance 3452, 3552 (e.g. metals such as Mo, W, Cu, Ta)and low impedance materials 3451, 3551 (e.g., dielectrics such as toform acoustic reflector above acoustic resonator device). FIG. 35 alsoshows a first electrode 3561 horizontally coupled to the first topelectrode 3541 and a second electrode 3562 vertically coupled to thesecond top electrode 3542. The intrinsic device is marked as 3501. Ofcourse, there can be other variations, modifications, and alternatives.

FIG. 36 illustrates circuit diagrams of the integrated reflectorstructure with the single crystal acoustic resonator device of theaforementioned Figures. This illustration is merely an example, andshould not unduly limit the scope of the claims herein. As shown,circuit 3601 is a block diagram with the piezo membrane 3622 sandwichedbetween the first top electrode 3661 and the second top electrode 3662.The connection area 3603 of block diagram 3601 is represented in thecircuit diagram 3602, showing an equivalent circuit configuration.

In an example, the present invention can provide an acoustic resonatordevice comprising a bulk substrate member, having a surface region, anda thickness of material. In an example, the bulk substrate has a firstrecessed region and a second recessed region, and a support memberdisposed between the first recessed region and the second recessedregion.

In an example, the device has a thickness of single crystal piezomaterial formed overlying the surface region. In an example, thethickness of single crystal piezo material has an exposed backsideregion configured with the first recessed region and a contact regionconfigured with the second recessed region. The device has a firstelectrode member formed overlying an upper portion of the thickness ofsingle crystal piezo material and a second electrode member formedoverlying a lower portion of the thickness of single crystal piezomaterial to sandwich the thickness of single crystal piezo material withthe first electrode member and the second electrode member. In anexample, the second electrode member extends from the lower portion thatincludes the exposed backside region to the contact region. In anexample, the device has a second electrode structure configured with thecontact region and a first electrode structure configured with the firstelectrode member.

As shown, the device also has a dielectric material overlying an uppersurface region of a resulting structure overlying the bulk substratemember. The device has an acoustic reflector structure configuredoverlying the first electrode member, the upper portion, the lowerportion, and the second electrode member. As shown, the acousticreflector structure has a plurality of quarter wave layers configuredspatially within the dielectric material.

FIGS. 37 and 38 illustrate a reflector structure (3700, 3800) configuredon the single crystal acoustic resonator device in an example of thepresent invention. This illustration is merely an example, and shouldnot unduly limit the scope of the claims herein. As shown, the devicehas similar features as one of the prior examples (FIGS. 24-32).Additionally, the device is configured with a reflector structureincluding alternating quarter-wave layers of high acoustic impedance3752, 3852 (e.g. metals such as Mo, W, Cu, Ta) and low impedancematerials 3751, 3752 (e.g., dielectrics such as to form acousticreflector above acoustic resonator device). FIG. 38 also shows a firstelectrode 3861 horizontally coupled to the first top electrode 3841 anda second electrode 3862 vertically coupled to the second top electrode3842. The intrinsic device is marked as 3801. Of course, there can beother variations, modifications, and alternatives.

FIG. 39 illustrates circuit diagrams of the integrated reflectorstructure with the single crystal acoustic resonator device of theaforementioned Figures. This illustration is merely an example, andshould not unduly limit the scope of the claims herein. As shown,circuit 3901 is a block diagram with the piezo membrane 3922 sandwichedbetween the first top electrode 3961 and the second top electrode 3962.The connection area 3903 of block diagram 3901 is represented in thecircuit diagram 3902, showing an equivalent circuit configuration.

In an example, the present invention can provide an acoustic resonatordevice comprising a bulk substrate member, having a surface region, anda thickness of material. In an example, the bulk substrate has a firstrecessed region and a second recessed region, and a support memberdisposed between the first recessed region and the second recessedregion.

In an example, the device has a thickness of single crystal piezomaterial formed overlying the surface region. In an example, thethickness of single crystal piezo material has an exposed backsideregion configured with the first recessed region and a contact regionconfigured with the second recessed region. The device has a firstelectrode member formed overlying an upper portion of the thickness ofsingle crystal piezo material and a second electrode member formedoverlying a lower portion of the thickness of single crystal piezomaterial to sandwich the thickness of single crystal piezo material withthe first electrode member and the second electrode member. In anexample, the second electrode member extends from the lower portion thatincludes the exposed backside region to the contact region. In anexample, the device has a second electrode structure configured with thecontact region and a first electrode structure configured with the firstelectrode member.

As shown, the device also has a dielectric material overlying an uppersurface region of a resulting structure overlying the bulk substratemember. The device has an acoustic reflector structure configuredoverlying the first electrode member, the upper portion, the lowerportion, and the second electrode member. As shown, the acousticreflector structure has a plurality of quarter wave layers configuredspatially within the dielectric material.

FIG. 40 illustrates simplified diagrams of a bottom surface region andtop surface region for the single crystal acoustic resonator device inan example of the present invention. As shown, FIG. 40 includes a topview 4001 and bottom view 4003, each with a correspondingcross-sectional view 4002 and 4004, respectively. These views show aresonator device similar to those described previously. A piezo membrane4020 is disposed overlying a substrate 4010. The top side of the deviceincludes a first and second top electrode 4041, 4042. The etchedunderside of the substrate includes a bottom electrode 4043. Of course,there can be variations, modifications, and alternatives.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A method for fabricating an acoustic resonatordevice comprising: providing a bulk substrate member, having a surfaceregion, and a thickness of material, the bulk substrate having a firstrecessed region and a second recessed region, and a support memberdisposed between the first recessed region and the second recessedregion; forming a thickness of single crystal piezo material overlyingthe surface region, the thickness of single crystal piezo materialhaving an exposed backside region configured with the first recessedregion and a contact region configured with the second recessed region;forming a via through the thickness of the single crystal piezo materialin the contact region of the thickness of single crystal piezo material;forming a metal pad in the via through the thickness of single crystalpiezo material; forming a first electrode member overlying an upperportion of the thickness of single crystal piezo material; forming asecond electrode member overlying a lower portion of the thickness ofsingle crystal piezo material to sandwich the thickness of singlecrystal piezo material with the first electrode member and the secondelectrode member, the second electrode member extending from the lowerportion that includes the exposed backside region to the contact region,the second electrode being coupled to the metal pad in the via throughthe thickness of single crystal piezo material; forming a dielectricmaterial overlying an upper surface region of a resulting structureoverlying the bulk substrate member, wherein the resulting structureincludes at least the first and second electrode members; and forming anacoustic reflector structure configured overlying the first electrodemember, the upper portion, the lower portion, and the second electrodemember.
 2. The method of claim 1 wherein the support member isconfigured in a plane coincident with a bottom surface region of thebulk substrate member.
 3. The method of claim 1 wherein the supportmember is configured in a plane off-set and recessed in reference to abottom surface region of the bulk substrate member.
 4. The method ofclaim 1 wherein the single crystal piezo material being characterized byX-ray diffraction with clear peak at a detector angle (2-Theta)associated with single crystal film and whose Full Width Half Maximum(FWHM) is measured to be less than 1.0°.
 5. The method of claim 1material wherein the single crystal piezo material is selected from atleast one of AlN, AlGaN, InN, BN, or other group III nitrides; andwherein the single crystal piezo material has a thickness of greaterthan 0.4 microns, the single crystal piezo material being characterizedby a dislocation density of less than 10¹² defects/cm².
 6. The method ofclaim 1 further comprising forming a first electrode terminalelectrically coupled to the first electrode member; and forming a secondelectrode terminal electrically coupled to the second electrode member.7. The method of claim 1 wherein the first and second electrode memberscomprise a tantalum or molybdenum material; and wherein the substratecomprises silicon, gallium arsenide, gallium nitride, aluminum nitride,or aluminum oxide.